Volkswagen Repair: knocking sound, vw vanagon, wheel bearings

Question
Hi
I own a VW vanagon westfalia, 1991. It has started making a knocking or popping sound, coming from the front underneath the van. Usually when turning and mostly at lower speeds, the sound itself speeds up and slows down with the speed of the vehicle.
Any idea what this could be?
Thanks
adrianne

Answer
Is this a front wheel drive vehicle.  Turn the wheel hard over and look past the tire to see if there  is an axle shaft. At the end near the wheel you will see a rubber "boot" that should be free of black grease on the outside.  If it is greasy, then the boot is ripped and dirt got inside. it will be that joint.  Check the other side for the same. If neither are ripped it is a matter of getting the vehicle off the ground and rotate the wheels via the axle to see which one is binding or is loose more than the other.  This is a job you(male types) can do yourself but you do need some tools and a smattering of patience)it is quite awful to do.   I am fortunate to be able to buy the whole shaft with both joints on for less than 1 cv joint and swap it with my own when that problem happens.  Sure, I may buy a bad one, then, again,maybe no. If so, then you constant velocity joint is (and there is 4 of them)failing. It will be an outer.  If you need to replace one, do the other outer as well.  When that goes, Boom, you stop dead.
  You've narrowed it down to a rotational noise.  
The only other possibility is wheel bearings